The present invention relates to a tire/wheel assembly which enables run-flat traveling and to a run-flat support member employed therein. More specifically, the present invention relates to a tire/wheel assembly and a run-flat support member, which are designed to be lightened without losing durability thereof for run-flat traveling.
To meet the demand from the market, numerous techniques have been proposed to enable a certain degree of emergency traveling even when a pneumatic tire is punctured while driving a vehicle. Among those numerous proposals, the techniques proposed in Japanese Patent Laid-Open Publication No. 10-297226 and Published Japanese Translation of a PCT Application No. 2001-519279 enable run-flat traveling by fitting a core to a rim in a cavity of an assembled pneumatic tire and supporting a flat tire with the core.
The foregoing run-flat core has an open-leg-structured circular shell including a support surface thereof extended toward the periphery of the tire and leg portions along each side of the support surface. The run-flat core is constituted by having elastic rings attached to both of these leg portions so that the core is supported on a rim through the elastic rings. The advantage of the run-flat core is that the available rims and wheels in the market can be used as their own, without any particular modification. Thus, the core can be accepted to the market without causing difficulties therein.
The run-flat core is required to be lightened to the maximum feasible extent since the run-flat core is a factor in increasing the vehicle weight. However, it is difficult for the run-flat core to exhibit satisfactory strength if the run-flat core is merely thinned. For example, if the elastic rings are thinned in a shell axial direction, the circular shell will be unstably supported by the elastic rings. Thus, durability of the run-flat core for run-flat traveling is reduced. In addition, the elastic rings are required to be capable of supporting a load in a shell radial direction during run-flat traveling. However, at the same time, the elastic rings are required to be excellent in the workability in tire-to-rim fit, in which the elastic rings have low resistance to bending deformation in the shell axial direction when fitting the tire to the rim.